Trunking system for radiodistribution



March 19, 1929. E. E. CLEMENT TRUNKINQG SYSTEM FOR RADIODISTRIBUTION 6 SheetsSheet 1 Filed Jan. 1925 fiavargior,

March 19,1929. E. E. CLEMENT TRUNKING SYSTEM FOR RADI ODISTRIBUTION Filed Jan. 6, 1925 6 Sheets-Sheet 2 March 19, 1929. E'QLEMENT 1,706378 TRUNKI NG SYSTEM FOR RADIODISTHIBUTION Filed Jan. 6, 1925 6 Sheets-Sheet 5 Mapuwme Mom/M7015 March 1929- E. E. CLEMENT TRUNKING SYSTEM RADIODISTRIBUTION Filed Jan. 6, 1925 II II 6 Sheets-Sheet 4 March 19, 1929, E. E. CLEMENT TRUNKING SYSTEM FOR RADIODISTRIBUTION Filed Jan. 6', 1925 V e Sheets-Sheet 5 0 WWW-EH04? I l 1 .B 67

March 19, 1929. ,E. E. CLEMENT TRUNKING SYSTEM FOR RADIODISTRIBUTION 6 Sheets-Sheet 6 Filed Jan. 1925 Patented Mar. 19, 1929. V

UNITED STATES EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT COLUMBIA, A SSIGNOB '10 ED- WARD F. COLLADAY, OF WASHINGTON, DISTRICT OF COLUMBIA.

TRUNKING SYSTEM FOR 'RADIOIDISTRIBUTION.

Application filed January My invention relates to systems of radio broadcast distribution, and has for its objects in particular to produce a subscribers instrument and to relate the same to central ofiice apparatus in such manner that programs may be originated, relayed and d1 stributed over a wide area, in a systematic and orderly manner; so that ultimate receiving stations may be controlled and operated as subscribers stations and the programs dis tributed may be confined to said subscribers stations and not be available for outside receiving stations not forming a part of the system; so that subscribers may select different programs or 'diflerent items from different programs as time of rendition proceeds; so that subscribers may obtain any item produced and distributed from any part of the system to any other part of the system and within the range of their selective apparatus; so that while the subscribers may get the full benefit of amplification and the use of vacuum tubes in receiving and amplifying, yet their stations will be tubeless, that is to say, all the tubes pertaining to subscribers receiving apparatus shall be located at central points, which may be also the final distributing points through which the programs or signals are given to the subscribers; so that all reception by the subscriber of programs or program items selooted by him, shall be differentially metered according'to the value fixed upon them by the broadcasting authorities, and automatically recorded at the rates so determined; so that a subscriber may have nothing at his station but standard telephone apparatus, connected and operating in conjunction with telephone line circuits, but capable of operating a loud speaker when desired; and finally so that the entire control, supervision, metering, current supply, installation and maintenance of subscribers instruments will be from organized central stations provided with expert operators.

I attain these and other objects which will sufiicicntly appear hereinafter by connecting all the subscribers stations in groups to localized central oflices or exchanges, supplying such exchanges with broadcast matter over'trunks from a relay broadcast service station having receiving instruments which may be of any suitable type, such as those described in my prior copending applica- 6, 1925. Serial No. 913.

tion, Serial No. 746,357, filed October 28,

1924; providing line circuits enterin a central station with vacuum tubes, one line, constituting terminals of the lines for radio distribution; and finally connecting these distributing tubes, which may be audio for each frequency amplifiers, to the trunks leading from the appropriate receiving devices at the broadcast service station, and employing these connections as well as the conditions brought about by the subscribers, to operate meters, and to enable the central oflice operators to variously control, supervise, etc.

In my prior application aforesaid, distri-.

transmitted either by Wire carriers or as modulations on high frequency or short radio carrier waves. In other words, the original modulations, unchanged, are passed along and relayed from point of origin, on their long carrier waves, to the ultimate points of reception, being multiplied and amplified on the way so that all transmission losses are neutralized or compensated, and the subscribers with very simple and inexpensive instruments can receive from all points, near or far, as efliciently as though they had the best and most powerful receiving instruments available. It is the purpose of the present invention to carry this a step farther, by making it possible for absolute uniformity to be obtained in the ofiiciency of distribution and ultimate receiving, as well as the greatest economy inv apparatus, costs of installation and maintenance, and cost of service. I do this by distributing over the subscribers wire lines, at audio ire-- quencies, and determining the volume of current and the efficiency of transmission over each line individually, by using a line valve or tube at the central station. For selective purposes, the subscriber is provided with a dial or other means of producing impulses or grams receiving simultaneously, the commonbatteries at the central ofiice may be divided into groups, one for each program, so that only those subscribers lines will be tied together, even through their tubes, which are taking the same program. Cross talk or leakage from line to line is thus avoided.

This inventionis applicable to manual, automatic or so-called semi-automatic or automanual telephone systems, as will sufiiciently appear hereinafter. The 'main underlying principle involved is that of dis ,tributing from a broadcast service station through a central station to a plurality-of subscribers lines by means of individual llne tubes or valves, so that each line may have its own self-contained receiving unit, needing only excitation by the central ofiice relay transmitter.

The method I have found most satisfac' tory in practice is to include one stage of audio amplification in each relay set or transmitter, the line tubes constituting a second stage. Current carrying capacity and power of the line tubes may be varied WitllIIl wide limits, affording any amount of energy for transmission and any class of service that is desired. If the exciting circuits connected to any one bus at one time are too many, the busses may be banked by means of tubes in parallel as well understood in the art. In this case, each relay transmitter at the broadcast service station would preferably have a detector tube connected through a transformer to a luralit I of audio amplifier tubes in paralle constlv tuti ng a multiplied first stage, the plate circuits of which would be connected to the bus through a suitable transformer.

Regulation of the current flow from the B or plate battery through each bus during program transmission may be obtained by means known in the art and usuall manipulated by an operator ata transmltting station.

Some modifications can be made in the arrangement and many modificationsin the detail of circuit and design, but I feel the principle as stated to be novelin its application and original with myself, and I shall claim the same accordingly. 1

panying drawings, in which: 7

Figs. 1 and 2 indicate, diagrammatically, the telephone exchange portion, and broadcast distributing portion, respectively, of my combined telephone exchange and broadcast distributing system.

Fig. 3 is a diagram of the broadcast service station.

Fig. 4 is a modification of the circuit arrangement of Fi 2.

- Fig. 5 is a modified form of the switch arrangement of Fig. 4.

Fig. 6 is a diagram showing the operative relation and connections between different stations in. a general system of broadcast distribution embodying the invention.

Fig. 7 is a dia ram of a trunking arrangement for exten ing a subscribers line circuit outside the local central station.

Fig. 8 is a schematic diagram showing the general arrangement for distribution of 'a broadcastprogram through an amplifier circuit common to a plurality of lines and second stage amplifier tubes and circuits individual to the subscribers line.

Referringto the drawings in detail, and

first to Fig. 1, this shows the essential circuits of an ordinary telephone exchange system in which A is a subscribers station connected by line wires (SQ-70, to the central station G where they terminate on multiple jacks J. Similarly the multiple jacks J at the left of the figure represent the terminals of another substation line. These jacks are arranged to be interconnected through the usual answering and calling plugs PP forming the terminals of" the usual common battery cord circuit shown. The central office terminals of each line are provided with the usual line relay L, line lamp L and cutoff relay L Where-service is to be metered a recording meter'M is also individually associated with the line. Thus, the circuit arrangement here shown is that of the standard multiple switchboard, common battery, telephone exchange system, and as such is wel understood in the art further detailed description thereof will be here deferred and broug t out later in the description of operation. In addition to the usual line terminal multiples 1, .2 and 3, representing multiples of the tip, sleeve and test or cutoff circuits, respectively, I provide a fourth' conductor 4 leadin from a contact on the line relay alon wit the multiple'conductors 1, 2'and 3 to t e broadcast distributing system diagrammed in Fig. 2.

Fig. 2 shows the broadcast distributing system of which the portion to the left of the dotted line is situated at the central oflice and connected with the 'subscribers telephone line terminal apparatus of the telephone central 0 (Fig. 1) through conductors 1, 2, 3

dotted line in'Fig. 2 is situated at the subv p v V and 4, while the portion to the right of the My invention is illustrated in the accom- 5 and 6. In Fig. 2 the subscribers line multiples 1-2 terminate in contacts 78 of an automatic selector switch S. This switch is of a type well understood in the automatic telephone art in which movable contacts or wipers such as 7 and 8 are carried on a shaft 10 biased in a given normal position by a spring or other suitable means not shown and arranged to be stopped around by a stepping magnet 11 through a stepping pawl 12 and a ratchet 13. Also, as is usual with such switches, it is provided with a dog 14, arranged to be thrown out of engagement with the ratchet 13 and to throw the'stepping pawl 12 out of engagement when the dog is stepped by the actuation of the release magnet 15, the energization of the re, lease magnet 15 effecting the tripping of the dog 14 through an extension 16 on its armature 17 pivoted at 18. 'To hold up the armature extension 16 until the switch has released, a trip detent 19 is provided which is pivoted at.20 and arranged to be held normally out of engagement with the hook 21 on the armature 17 by a cam 22 on the switch shaft which permits the detent 19 to move into operative relation with the hook 21 whenever the switch is in off-normal position. lflounted on the switch shaft 10 are other pairs of wipers 23-24, 25-26, and 2728. The switch S is provided with a contact bank containing rows of contacts 30, 31, 32 and 33 arranged to be engaged by the switch wipers 78, 2324, etc., successively in the direction indicated by the adjacent arrow, it being understood that while the drawing, which is purely diagrammatic shows the contacts arranged in a straight line they are in practice arranged in a circle concentric with the switch shaft so as to permit the switch arms to sweep across them in the rotation of the shaft. While only three vertical rows of contacts are here shown it is to be understood that they may be more or less in number and that in any case the first few vertical rows of contacts are left blank or disconnected, for example, in the present case the first five, leaving the sixth vertical row of contacts the first ones that are connected with the operating circuits so that the switch must make five steps before effecting any circuit connections, after which the wipers will be moved successively to the sixth, seventh and eighth vertical rows. The purpose of providingthis lost motion or blank steps will be made clear in the description of operation. The switch wipers 2324 connect with the adjacent terminals of the winding 34-35 of a repeat-- ing coil 36, the remote terminals of which windings connect to the plate and filament of the audion tube 37. The switch wipers 25 26 connect to the grid and filament of the tube 37, while the wipers 26 and 28 form the terminus of the filament ofthe tube 37.

The wiper 27 is connected to the multiple being connected respectively to the remote terminals of the coils 38 and 39 of the repeating coil 36 through the conductors 40 and 41, the conductor 41 connecting with the coil 39 through a sleeve or line supply relay 42, shunting resistance 43 and conductor 44. The adjacent terminals of the coils 38 and 39 are connected to the plus and minus side of the exchange common battery B through conductors 45 and 46, and bus conductors 47 and 49, respectively. In the horizontal row of contacts 31, the sixth, seventh and eighth pairs are connected individually to the batteries B", B and B respectively. In the horizontal row of contacts 32, the sixth, seventh and eighth airs areconnected, respectively, to the distributing buses 66, 67 and 69, the lower contacts of the sixth, seventh and eighth pair's being connected respectively to the bus wires of filament batteries F, F, and F respectively. In the horizontal row of contacts 33 the upper members of each pair are connected in multiple to the conductor 49 which supplies battery current for the test by its connection through repeat relay 50, conductor 46 and bus 48 to the central oifice common battery B. The lower contact members of the horizontal row 33 are connected individually to the upper bus wires of the different filament batteries F", F, and F Thus the batteries B, B and BZthe program busses 66, 67, and 68,.and the filament batteries F, F and F are associated individually with the sixth, seventh and eighth vertical rows of contacts, respectively. The stepping magnet 11 and release magnet 15 .have their windings connected in multiple,

one side to ground and the other side through conductor 51 to an impulse wire 40 leading into Fig. 1 where it terminates in a front or normally open contact 52 of the line relay L, which contact is engaged by the armature 53 connected through Wire 54 to the exchange common battery B. The conductor 51 is also connected in multiple to a normally open contact 55 engaged by the armature 56 of the relay 50,the armature 56being connected by Way of conductors 46 and 48 to the exchange common battery B. The repeat relay 50 is controlled by the sleeve relay 42 through the armature 57 which is arranged, as shown to. close a shunt ifi'erent program around the winding of the relay 50 by Way of resistance 58, armature 57 and conductor a mate receiver.

cuit through the line multiples 56,' winding 60 of the booster coil 61, transmitter 62 and automatic dial 63, while connecting the subscribers broadcast telephone receiver 64 across the line multiple 5-6 in series with the coil 61-65 andtelephone condenser 266. The program busses 66, 67 and 68 are supplied with broadcast matter from the broadcast service station Fig.- 3, over trunk wires T", T and T respectively which form the output terminals of program transmitting devices P, P and P preferably radio receivers of a type adapted to receive .radio tion is effected through the 'audion tube 37 individual to each line.

a In the operation of the arrangement shown in Figs. .1, 2 and 3, the subscriber at stationA operatively connects his broadcast receiving or extension set A to the line by inserting the receiver plug P in the jack J 2 which connects his receiver 64 across the line multiples 5 and 6 through the booster coil windings 60-65 and condenser 266 in series, and closes a path for direct current between the multiples 5 and 6 through coil 60, lower spring of jack J transmitter 62, and automatic dial 63. This energizes the subscribers line relay at the central ofiice in the usual manner by current from the central office common battery B,

which' energizing circuit may be traced from the grounded side of central oflice common battery B, conductor 68, right hand winding of line relay L, line conductor 69, to subscribers substation A, line multiple 5, to subscribers broadcast receiving set A (Fig. 2), coil 60, transmitter 62,

"contacts of dial 63, conductor 6, 70, left hand winding of line relay L, and back to the battery Ba Energization of the line relay energizes the line lamp L by closure of a local circuit which may be traced from the battery B through elements 54,11 71, 68 and back to battery B. This causes the line lamp L at the telephone operators switchboard to glow, but only for a moment as the subscriber wanting broadcast service will immediately operate'his dial to break and make his line circuit a certain number of times according to the particular program he desires which breaks and makes will cause his line lamp to flicker instead of glowing steadily and so indicate to the telephone operator that the subscriber is not calling for a telephone connection but is automatically setting up his connection for broadcast reception. As the dial 63 is of the well known type used in automatic telephony and well understood in the art,

it will not be necessary to describe the same ping magnet 11 and release magnet 15 in multiple and thence through ground back to the grounded side of battery B. It is to be noted here that the release magnet 15 is made sluggish in its action so that it will not respond to the energizing current until after a lapse of time much-longer than the interval between the breaks and makes of the subscribers dial 63 so that when the subscriber first closes his circuit, as just described, thestepping magnet 11 will first operate to step the switch 9 around one step releasing the detent 19 after which, the time period of the release magnet 15 having lapsed, this magnet will actuate its arma ture to remove the hook 21 up into engagement with the detent 19 and the extension 16 into engagement with the dog 14 which disengages the dog from the ratchet 13 and also throws the pawl 12 out of engagement with the ratchet, thus causing the switch to release and return to normal position whereupon the cam 22 will throw the detent 19 out of engagement with the hook 21 and leave the armature 17 free to return to normal position when the magnets become deenergized. 'In the case of a call for telephone connection this deenergization of the magnets would occur when the telephone operator, in answering, inserts the plug P in the jack which would operate the line cut-ofi relay L in the usual manner causing the line relay L to retract its armature 53 and open the circuit of the stepping and release magnets -11 and 15. To prevent the subscribers broadcast selector switch 9 from being stepped around and'connecting broadcast matter on to his line due to one or more accidental breaks in. his line circuit while the subscriber is waiting for telephone operator service, the selector switch 9 is provlded with several blank contacts preceding those representing the difierent in Fig. 2, where theblank contacts are not shown, it being understood that the switch must make five steps before its wipers engage the first set of active contacts. Thus if the subscriber, while waiting for an operator should accidentally, momentarily open his line or impatiently. operate his switchhook a few times, the connector switch would simply step around over a few of the blank contacts and release as before described when the operator plugged in with her answering plug. Returning now to the subscribers selection of a desired broadcast program, the subscriber, shortly after the initial closure of his line effected by his insertion of the plug P in the jack J and before the line lamp has been energized sufliciently long to indicate a telephone call to the operator, sets his dial to a number corresponding to the number of the, broadcast program he wishes to receive, which in the present case would be some number above five, and permits the same to release producing a number of breaks corresponding to the setting of the dial. Assuming the setting to be eight, the dial upon release will cause the line circuit to be momentarily opened eight times. The first five breaks inthe line circuit will cause the armature 53 of the line relay to open and close its connection with the contact 52 five times, thus step ing the selector switch around to the fi th contact, the period of closure of the contacts 52-53 being sufficiently brief to "prevent actuation of the release magnet 15. Upon the sixth momentary break and subsequent make of the'line circuit, the switch 9 will step on to the sixth or first vertical row of active contacts whereupon the line cut-off relay L will be energized and the control of the stepping magnet 11 transferred from the line relay to the sleeve relay 42 of the switch circuit. The energizing circuit of the cut-off relay L may be traced from the common battery B (top of Fi 2), bus wire 48, conductor 46, winding 0 repeat relay 50, conductor 4?, upper member of the sixth contact of hor1- zontal row 33, switch wiper 37, conductor 3, into Fig. 1, line cut-ofl relay L conductor 69 to grounded side of the common battery B. Energization of repeat relay 50 causes its armature 56 to engage the contact 55 thus maintaining the stepping magnet 11 energized by current from battery B through circuit elements 48, 46, 56, 55, 51, 11, to ground and back to battery B, while the en-' ergization of the cut-off relay L .(Fig. 1) disconnects the line relay L in the usual manner which becoming deener ized releases its armatures 71'53 extinguis ing the line lamp and opening the circuit through conductor 4. Simultaneously with the energization of the cut-off relay L? and repeating relay 50, the sleeve relay 42 is energized by switch wipers 2526 and the eighth current from the common battery B through the circuit elements 48, 46, 39, 42, 41, lower member of the sixth contact in the horizontal row 30, switch wiper 8, line'multiple 2 into Fig. 1, line wire 70, multiple wire 6, into Fig. 1, through circuit elements 63, c2, 60, 5 into Fig. 2, 69, 1, into Fig. 2, 7, 4.0, 38, 45, 47, and back to the rounded side of the common battery B. %nergization of sleeve relay 42 causes its armature 57 to be attracted and complete a shunt around the winding of repeat relay 50 by way of circuit elements 58, 57 and 59, which shunt causes the relay 50 to become deenergized and retract its armature 56 opening the circuit of the stepping magnet 11 and causing it to return to normal ready for the next step. The next or seventh momentary 'break in the subscribers line circuit, which follows immediately, effects a momentary release of the armature 57 of sleeve relay 42 which causes a momentary energization of the "repeat relay 50 which in turn effects a I momentary closure of the contacts 56-50 and a momentary energization of the stepping magnet 11 to step the switch wipers around to the seventh vertical row of contacts. The energizing circuit of the stepping magnet may be traced from the common battery B through circuit elements 48, 46, 56, 55, 51, and 11 back to the grounded side of battery B. Similarly, the next or eighth momentary break in the line causes the stepping magnet 11 to be again momentarily energized and step the switch wipers around into engagement with the eighth vertical row of contacts.

After the eighth momentary break in the line circuit the subscribers dial '63 comes to rest and maintains the line circuit closed. The line now being closed, the sleeve relay 42 is maintained energized which maintains the repeating relay 50 deenergized by virtue open at the contacts 55-56. The switch wipers thus come to rest on the eighth vertical row of contacts, maintaining the input terminals of the subscribers line tube 37 in operativeconnection with the bus wires 68 of the program transmitter P through air of contacts in the horizontal row 32. Eurrent is supplied to the output or plate circuit of the tube 37 from battery B individual to the program transmitter P over circuit elements 72, 73, 23, 74, 34, plate of tube 37, filament of tube 37, 75, 35, 76, 24, 77, 78,

back to batter B. As the coil 36 is a re-' peating coil 0 the well known type having the four'windings 34, 35, 38, 39 on a common magnetic core the output or plate circuit of the tube 37 is coupled to the subscribers line through the coils 38-39 which are included in series in the subscribers line circuit as hereinbefore traced. The filament circuit of the subscribers audion tube 37 may be traced, from filament battery F individual to the program transmitter P over the circuit elements 79, lower member of bus wire 68, 26, filament of audion tube 37, filament rheostat 80, 28, 81, 82, back to battery F As the winding 60 of the booster coil 61 at the subscribers broadcast receiving set -A is included in series in the line, the broadcast matter coming thereover is repeated in the winding 65 which reproduces the signal in the subscribers receiver 64 over a circuit which may be traced from 65, through cirjcuit elements 66, 63, 62, and through the receiver 64 back to winding65 by way of the plug and jack connection P As the sleeve relay 42 is held energized during the subscribers use of his line for receiving broadcast, should a telephone operator test one of his multi 1e jacks in the usual manner before establis ing a connection therethrough to his line, instead of the ordinary busy test of a click in the ear, she will receive a special tone test which will indicate that the line is not busy for telephone use but is being used for the reception-of broadcast so that if the call is an emergency one the operator .may plug in regardless of the busy condition Thus a special tonetest is e'fiected by the usual tone test a paratus indicated in Fig. 2 as consisting o the inductance 87 connected in series with a circuit breaker 88 and inductively related to the coil 58 in series in the test circuit. The energizing circuit of the coil 87 may be traced from the common battery B through the circuit elements 48, 46, 87, 88, backthrough ground to the battery B.

' When the subscriber wishes to discontinue the broadcast reception he withdraws the plug P which opens the line circuit at the ack contact 89. This deprives the sleeve relay 42 of current whereupon its armature 57 is retracted removing the shunt from the repeating relay which thereupon becomes energized and'closes the circuit of both the contact 55.

stepping magnet and the relay magnet through connection of the armature 56 with Thiscircuit may be tracedfrom battery B through the circuit elements 48, 46, 56, 55, 51, 11, and 15 in'multiple to ground and back to the battery B. After- Switch and until the switch reaches the normal position whereupon the cam 22 operates to disengage the detent 19 from thehook 21 and permit all parts of the switch to return to the normal position shown. When radio broadcast service on a basis of time use, a meter controlling actuator 90 (Fig. 2)

is arranged. to control the subscribers tele phone meter M (Fig. 1 through the operative connection of the switch circuits of Fig. 2 with the subscribers central ofiice line terminal circuits. This control circuit may betraced from'the meter generator 91 (Fig. 2'). through commutator 90, switch 92, bus wire 93, switch 94, wire 49, the upper member of one of the contacts in the horizontal row 33, wiper 27, test wire 3, into Fig. 1, wire 95, high voltage winding 96, of the meter M,

to ground and back to the grounded side of the meter generator 91 (Fig. 2). When the meter armature- 97 is retracted a sufiicient distance to close the contact 98 the low volt? age winding 99 of the meter M is closed thus aiding in the further attraction ofjthe. armature and the actuation of the meter as well understood in the art, which actuation will be repeated at intervals according to -the intervals of theclosing and opening of the circuit meter commutator 90.v These periodic registrations of the meter during use of the broadcast apparatus will of course be added to those produced by the actuation of the usual, telephone operators metering key 100, so that the subscribers'use of the broadcast service is charged in the same units as that of the. telephone use and the amount of service represented by a unit charge varied according to, the, speed of operation of the commutator 90. Where the service to some f the lines is to be given free the switch 94 lndividual to the line is opened and where the service is to be given free to all or a group. of lines the switch 92 is opened to disconnect the commutator from the bus 93 commonto all or a group as the case may be.

' To aflord communication between the broadcast service station and a subscribers station, the broadcastservice station is provided with telephone lines 230 and 231, each terminating at the service station in the' I usual telephone set, as represented at 232 and 233, and at the telephone central station in suitable line terminal apparatus such as the jacks 234 and 235. Also at the broadcast service station, the lines230 and 231 are provided with multiples 238 and 239 terminating in jacks 240 and 24:1 to enable any serving to localize and fix the former. This use of the system is of value in certain classes of advertising and sales work as Well as entertainment. To enable original matter or local announcements to be sent out from the broadcast service station, a microphone circuit 242 is provided which terminates in a jack 243 for connection with any one of the modulators of the transmitters P P or P Referring now to Fig. 4, this is similar to Fig. 2, just described, except that the line multiples 12 are permanently connected to the outside terminals? of the coils 38 and 39 and the battery connection to the inside terminals of these coils controlled through the upper pair of wipers 78 of the switch 9, and the horizontal row 30 of the switch bank contacts. 'Another difference is that the repeat relay is omitted and the stepping 'of the switch, after connection with the active contacts, controlled through a back or normally closed contact of the sleeve relay 42 connected to battery through an off nor mal switch 101 controlled by a cam 102 on the switch shaft 10 arranged to maintain the off normal switch closed only during engagement of the switch wipers with one of the sets of active contacts that is, from the sixth vertical row on. As this is a modifimomentary breaks in his line circuit, the

first six cause the liner relay to close the contacts 5253 six times which in turn effects six successive V energizations and deenergizations of the stepping magnet 11, the successiveimpulses being as before described, of too brief duration to cause actuation of the release magnet 15. The energizing circuit of stepping magnet 11 may be traced from battery B (Fig. 1) through circuit elements '53, 52, 4, into Fig. 4, 51, 11, and

through ground back to battery B. This causes the switch 9 to step around to the sixth vertical row of bank contacts whereupon the cut-ofi' relay L (Fig. 1) is energlzed by current from battery B (Fig. .4) through the circuit elements 58, upper contacts of row 33 of the switch bank contacts,

27, 3, L 68, to ground and back to battery B. At the-same time battery is supplied to' the subscribers line in series with the sleeve relay 42 over a path which may be traced from battery B (upper part of Fig. 4) through upper members of row 30 of the switch bank contacts, circuit elements 7, 140, 39, 42, 2, 70, to subscr'ibers station and back by Way of 69, 1, 38, 141, 8, lower contacts of row 30, back to battery B. The seventh break in the line, effected by the subscribers dial 63, effects a momentary deenergization of the sleeve relay 42 whose armature falling back produces a momentary closure of the circuit of the stepping magnet 11 whose energizing circuit may now be traced from battery B (Fig. 4), through wiper 7 to wire 140, as before traced, and thence through off normalswitch 101, the cam 102noW having moved into a position to close the same,

thence through circuit elements 103, 104, 105, 51, 11, and through ground back to battery B. Similarly upon the eighth break in the line circuit, the switch 9 is stepped again, this time onto the eighth vertical row of contacts, which connects theinput circuit of the subscribers line tube 37 onto the program bus wires 68 through the eighth pair of contacts in row 32 and switch wipers 25-26. The switch wipers 2324 engaging the eighth pair of contacts, connect the battery B individual to the number 8 program, through conductors 74 and 76 through the windings 34 and 35 of the repeat coil 36 to .the output or plate circuit of the subscribers line tube 37, While the switch wipers '7 and 8 maintain the connection with the battery B through the multiple contacts of row 33 and so supply current over the subscr'ibers line as before traced. Also, as in Fig. 2, the filament circuit of the subscribers line tube 37 will be supplied with current from the filament battery A individual to the number 8 program, the connections for this being the same as that of Fig. 2. Also, as in Fig. 2, the cut ofl relay, busy test and meter control circuit 3 is completed through wiper contact 27. The circuit of the cut off relay may- 90,142, 143, 27, 3, into Fig. 3, 95,

ating current may thus be traced through tobe readin connection'with Fig. 1, the con- 65 1 the source 91, through the circuit elements meter M, to ground and back to the source 91.

In Fig. 5, is shown diagrammatical, a switch circuit which is a'simplified form of the circuit arrangement of Fig. 4 in which the number' of switch wipers are reduced to a minimum by delegating the control of.

certain circuits which are common to all the program's, to a cam actuated switch operable to maintain said circuits closed only during switch is controlle the engagement of the switch wipers with the program contacts. In this, as-in the other switch arrangements previously de scribed, the contact bank of the switch is provided with several vertical rows of blank contacts, for example, five in number, not shown, for the purpose of permitting the switch to he stepped around several steps without efi'ecting connection with any program transmitters. switching arrangement which are similar to and perform the same function as con-e Parts of the present sponding'parts in the previously described.

bered. For example, the battery supply for the output circuit of the subscribers line their associatedcont'acts, and the metering circuit is connected throughwiper 27 and its associated contact, with-the meter actu-.

ating source. All of these circuits are to be connected with sources individual to a program and so their control is delegated to the wipers which change connection with-each step of the switch. Thus, circuit connections which are not individual to a program such as the connections efiecte'd through the multiple line conductors 12, test conductor 3, and impulse conductor 4, are controlled through the cam operated switch 145. This by the cam 146 carried by the switch shaft 10 to maintain the con: tacts open when the switch is in its normal position or has moved into a position in which its wipers are on any of the blank contacts, and will maintain its contacts closed in any position of the switch in which the switch wipers are in engagement with a set 'I of the program contacts. Another feature" characteristic to the present switch arrangement is the position of the individual meter IM individual to the switch circuit so as to meter only the use of the subscribersline for broadcast reception.- As with the other switchingdiagram, the present diagram is ductors 1, 2, 3, and 4 of Fig. 5 tying onto In the operation of this. arrangement, the

impulses sent over wire 4 from the subscribthe conductors 1, 2, ,3 and 4 of Fig. 1 respectively.-

ers line relay in Fig.1, pass directly to the stepping magnet 11 through conductor 146 lay 42 energized in series with the subscribers line and the cut off relay in Fig. 1 en'- ergized to disconnect the line relay, which now causes the further stepping of the switch to. be controlled through the sleeve 'relay as, a repeating relay responding to breaks inxthe subscribers line circuit. The

circuit of the cut off relay (Fig. 1) may be traced'from battery B (Fig. 5), supervisory lamp 147, conductor 148,- contact of switch 145, conductor 3', into Fig. 1, cut oil' relay Lflconductor 68 to ground and back to bat tery .B

energized and open th'ecircuit through the impulse conductor 4 as before described in connection with Figs. 1 and 2. At the same time the out off relay is deenergized tobring about the disconnection of the circuit through conductor 4, the sleeve relay 42 is, energized in series Withthe subscribers line by a circuit which may be traced from battery B through the circuit elements 39, 42, 2, 70, over the subscribers line and back by way of circuit elements 69, 1, 38, to battery The energization of the cut'oll re-- layll causesthe line relay L to become-deswitching arrangement, are similarly num- B. Upon the next momentary break in the subscribers line circuit the sleeve relay 42,

being energized in series therewith, is momentarily deprived of current which causes a momentary retraction of its armature,

which in turn closes the circuitofthe stepf ping magnet 11 which may be now traced from battery B through the circuit elements 104, 105, 146, 1 1, toground and back to battery B. Thus, each momentary break in the subscribers line circuit causes the switch to make one step. When the switch comes to rest with its switch wipers on the vertical program, the sleeve relay 42 remains energized maintaining a shunt around the lamp. ,147 through resistance 149 thus extinguishq ing the signal light. This is the'operating position of, the switch, and during the maintenance of this connection, assuming the switch wipers to be in contact with the verconnect the line rela which now causes the further stepping o the switch to be conrow of contacts corresponding to thedesired trolled through the sleeve relay as a repeating relay responding to breaks in the subscribers line circuit. The circuit of the cut ofl relay (Fig.1) may be traced from battery B (Fig. 5), supervisory lamp 147, conductor 148, contact of switch 145, conductor 3, into Fig. 1, cut off relay L conductor 68 to ground and back to battery B. The energization of the cut ofl relay L causes the line relay L to become, deenergized and open the circuit through the impulse conductor 4 as before described in connection with Figs. 1 and 2. At the same time the cut oil relay is deenergized to bring about the disconnection of the circuit through conductor 4, the sleeve relay 42 is energized in series with the subscribers line by a circuit which may be traced from battery B through the circuit elements 39, 42, 2, 70, over the subscribers line and back by way of circuit elements 69, 1, 38, to battery B. Upon the next momentary break in the subscribers line circuit the sleeve relay 42, being energized in series therewith, is mementarily deprived of current which causes a momentary retraction of its armature, which in turn closes the circuit of the stepping magnet 11 which may be now traced from battery B through the circuit elements 104, 105, 146, 11, to ground and back to battery B. Thus, each momentary break in the subscribers line circuit causes the switch to make one step. When the switch comes to rest with its switch wipers on the vertical row of contacts corresponding to the desired program, the sleeve relay 42 remains energized maintaininga shunt around the lamp .147 through resistance 149 thus extinguishing the signal light. This is the operating posit-ion of the switch, and during the maintenance of this connection, assuming the switch wipers to be in contact with the vertical row of bank contacts associated with the number 7 program, the individual, broadcast service meter will be intermittently energized in a circuit which may be traced from the meter energizing source 91, through commutator 151, switch 152, upper member of the bottom pair of contacts in the eighth row, switch wiper 27, conductor 153, meter IM to ground and back to the source 91. It will be noted here that by movement of the switch arm 152 to its right hand contact the meter will be controlled through the commutator151 instead of 152. .iss these commute-tors are arranged to close and open the circuit at different periodicity, the meter will be operated at a difierent rate thus making a different charge per hour for the service. For the urpose of assigning different rates to di erent programs the switches 152 and 154 included in the meter circuits of the different programs, respectively, are arranged, as shown, with different,

contacts connected with the difl'erent con"- mutators 150 and 151, respectively. Thus,

with the meter control commutators 150 and 151 associated with diflerent programs, the subscribers service charges as recorded b his broadcast meter IM will vary accor ing to the particular program taken by him. To enable the operator or supervisor having charge of a number of switching devices like the present one, to listen in on the subscribers line in the usual manner as in a telephone operators cord circuit for the purpose of communicating with the subscriber, a listening key K is provided arranged to connect a suitable listening set, not shown. The subscriber may apprise such supervisor of his wish for somespecial service by making several successive momentary breaks in his line circuit much in excess of that required for the stepping of the switch to any of the sets of program contacts during which the supervisory noticing the apparent constant flickering of the supervisory lamp 147, will operate the listening key K to ascertain the wants ofthe subscriber. To enable the supervisor to call the subscriber during the connection of his line through the switch mechanism, a special signaling key S is provided which is arranged to connect the inductance coil 154 across the subscribers line, which coil is inductively connected with the special tone signal circuit and thus puts the signal on the line to be heard in the subscribers loud speaker. To enable the subscriber to receive other broadcast items not on the programs to which his switch has access, the last vertical row of contacts in the switch have their program contacts such as 155 connected to a special program trunk 156 terminating in a jack 157 situated before what may be termed a special program operator who has access to trunks leading to other stations providing diflerent broadcast items, and who is also provided with means, such as telephone plugs forming the terminals of such trunks, for connection of any of said trunks to the special program contacts 155 through the jack 157, and short trunk 156. When the subscriber desires such special items he signals the supervisor in charge of the broadcast service by sending in the excessive number of breaks to signal the supervisor through actuation of the lamp 147 as before described, the extra number of breaks in the line circuit causing the switch to step around to the last vertical row of contacts and there come to rest, which disconnects the subscribers line from all of the regular programs and connects it through the switch wipers 2526 and special programs contacts 155 to the trunk 156 terminating in the jack 157. The supervisor listening in through use of the key K may now ascertain the wants of the subscriber and communicate the same to the special program operator over a suitable order C11- cuit not shown. The special program operator may then give the subscriber the program or item desired, by inserting the terminal plug of the appropriate trunk in the jack 157. This trunking arrangement for supplying thespecial programs from other stations will be clearly understood from an inspection of Figs. 6 and 7.

In Fig. 6 is diagrammed a portion of a general system of broadcast distribution comprising a master station A, broadcast service station B, subscribers central stations 0, and subscribers substations D, the relation of the stations A, B, and being the same as that described in my copending application Serial No. 746,357, filed October 28, 1924, except that the broadcast matter is transmitted from the B stations to the C stations as audio, or telephone currents over wire trunk lines T T and T The C stations, together with the subscribers substations D are provided with. means in the form of the circuits herein previously described in detail, for distributing the broadcast matter from the B stations to the subscribers stations D. The broadcast matter is originated or received from the other stations and put onto the program contacts of the subscribers selector switches over the program trunks T T and T by any known or other suitable form of apparatus symbolized at P P and P (Fig. 3), located at the B or service station.

In Fig. 7 is shown diagrammatically, the

. special trunking system enabling a subscriber at a D station to extend his line beyond his associated central station either directly, or through other stations of the system to some particular station for the purpose of receiving the broadcast program there originated or there available through suitable relay apparatus, for example, station B For this purpose, the special program operator at the C station is provided with a link circuit LC capable of connectino' a trunk terminal jack 160 with the subscribers special jack 157 (the same as 157 of Fig. 5) through a detector and amplifier unit DA. The jack 160 forms the terminal of a trunk 161 terminating in the B station B in the output circuit of a line amplifier tube 137 whose input circuit terminates in a jack 162. Similarly, the station B is provided with the circuit LB arranged to connect the jack 162 with the jack 163-to an amplifier unit IA,

the jack 163 forming the terminal of a trunk 159 which terminates in the output circuit of a line tube 237 at the A station, the input circuit of which tube terminates in the jack 164. At the A station is provided an amplifying link circuit LA the same as that of station B 'arran ed to connectthe .jack 164 with a jack 165 forming the terminal of a trunk 158 terminating in a line tube337, and jack 159 at station B in the same manner as that of the trunks 159 and 161. At.

the station B is provided a link circuit LB- similar to those at stations A and B and arranged to connect the jack 159 with the broadcast program apparatus 166 which may be a local source of broadcast matter or suitable relay device capable of relaying broadcast from some other station. Thus with the trunking system so described the subscriber at a D station may extend his line to the broadcast transmitter 160 of the station B over the trunking connection which may be traced from 160 through the trunking elements LB 159, 337, 158, 165, LA, 164, 237, 159, 163, LB, 162, 137, 161, 160, LG, 157, 37, to subscribers station D. In the present illustrattion this broadcast matter is transmitted from the station B over the trunks 158, 159, and 161 by carrier current, which is detected and amplified in the detector amplifier unit DA at the C stat-ion and from thence transmitted to the subscribers station at audio frequency or in the form of the original modulations, the amplifier units IA at the stations B A, and B being operable on the intermediate or carrier current frequency. In Figs. 6 and 7, the trunks 161, 159 and 158 are symbolical of a plurality of trunks which afford trunking distribution out from any of the stations to several G stations directly or through other stations. It is also to be noted that the outgoing terminal of each trunk line is provided with a line tube similar to that of the subscribers line tube which acts as an amplifier or relay so that throughout the several links, the line tubes or relays will operate to effect gradual amplification throughout the distribution thus avoiding the losses and the necessity for currents of large magnitude incident to long distant distribution without the use of increments of power between the source anddestination. It will be obvious that where conditions are favorable, the amplifiers IA at the intermediate stations A, B, etc. may

consist of but one step or may even be omit diagrammatically shown in Fig. 8, where a source of audio signals is indicated at 167, the signals of which are distributed through a transformer 168 and a group of several amplifier tubes 169 in multiple to the input side of a suitable coupling means such as the audio transformer 170, the output side of which distributes through several amplifier tubes 37 to as many trunks or line circuits 173. The line circuits 173 represent the subscribers lines such as the subscribers line 6970 of Fig. 1, while the amplifier tubes 37 represent the individual line tubes or relays such as 37- of Figs. 2, 4, etc. It will thus be seen that with this arrangement the amount of power in any of the intermediate circuits may be considerably less than the total amount of power distributed.

It is to be noted that the broadcast matter may if desired be put on the program contacts of the switch banks in the form of modulated carrier current, in which instance the subscribers line tubes 37 would be preceded each by adetector tube or other detecting means individual to the line.

In its broadest aspect this invention has to do with the distribution to telephone subscribers of radio programs or broadcast matter, through the usual distributive channels provided and employed in telephone exchanges, that is to say, switching means of some sort, with necessary line units such as the line tubes herein described, for passing the radio matter, in whatever form received, to and through the subscribers lines as audio frequency waves. It is to be understood,

' however, that many variations may be made in the form and design of the switching mechanism in the line units through which the broadcast matter is conveyed to the subscribers. Thus, instead of the equipment shown in Figs. 2 and 4 each line may have multiple jacks and the program busses may. have multiple jacks, with pairs of plugs manipulated by operators to make the desired connections. Such an arrangement will employ some signalling means between the subscriber and the operator. Another modification would be the provision of multiple jacks and line lamps on the radio board, one for each line, such line acks being constructed with pairs of terminals in the jack forced together when a plug is inserted so as to connect the line with the output side of its tube 37, through wires.40 and 41 of Fig. 2, providing contacts on the relay 42 to close the grid circuit 2526 to the program busses. If selection of program be desired, the switch shown in Figs. 2 and 4 would still be'employed, but would be actuated, both as to stepping and resorting by the relay 42 alone. With such a line jack, only dummy plugs would be required having no cord conductors, all contacts being made in the jack. In closing the line terminals of the jack to the output terminals of the tube circuit, provision is also made for closing the test and cut-off circuits to the test thimbles and the relay L of Fig. 1, through the wire 3. The operation of this arrangement would be verysimple, the subscriber desiring radio merely opening and closing his circuit rapidly, so as to flash his signal lamps on both the telephone and the radio switchboards, both of these lamps being connected in parallel in the same fashion as the lamp L in Fig. 1, controlled by the same line relay contact 71. The lamps flash, and

signal to both the telephone and the radio pulls up on line current, and gives the subscriber control of the switch magnets 11 and 15, so that he may step the switch around to pick out any program he pleases. In such case the'switch can be made very simple, having just as many contacts as there are program items to be selected at any one time, and arranging the latter so that as soon as the switch wiper has passed ofl" the last program contact, it will immediately be prepared to step on to the first one again, so that by continuous rotation any item of any program may be selected in any desired order.

The foregoing modifications still employ switches. It is further possible to eliminate the mechanical switching means, and use what the radio engineer would term coupling coils, or the equivalent. In a prior co pending application, Serial No.- 691,823, I have illustrated and described capacity wave collectors for transfer of energy, waves from one circuit to a nearby other circuit; and in the present case I may employ other such capacity coupling or electromagnetic coupling coils, which includes what is commonly known as a loop antenna. In this case it is advisable to modify the line re- .ceiving means for the radio impulse, employing instead of the tube 3'1 and the circuits thereof as shown in Figs. 2 and 4, a complete radio frequency receiving set with its output terminals connected to the line on its grid filament or input terminals terminating on a joint coupling coil, receiving waves from another coil or an antenna constituting the terminal of the program bus or busses typified in Figs. 2 and 4. A convenient arrangement of these line coils or loose couplers would be in a circular figure around the program antenna, and to save space the line terminals or coils may be arranged in circles one above the other, so as to form the waves, then by directional arrangement of the subscribers line coil, waves can be received at will from any of these antennae. Another modification, with either a movable or immovable line terminal coil, is selection by tuning. Assuming the frequencies on the different program antennae to be different from each other, then the subscriber by.

tuning his line to the coupling coil at central,

can select any one of the programs he dc sires. In principle, this arrangement involves the following: first, taking an ordinary radio receiving set away from the subscribers station and putting it at the central oifice, connecting him. to it through the wired line circuit from his station to central, but retaining the tuning elements, or variable capacity and inductance, one or both under the control of the subscriber (of course they may be at the subscribers station for direct, or at the central station for remote control by current variations over his line).

Then, having placed the receiving instrument at the central station and providing the subscriber With means for tuning it to collector, there is very little danger of ob-' jectionable radiation from the set.

The psychology of these modifications,

especially those employing radio coupling at the central station between the program busses and the lines, is simply that other 'things being equal, the first cost as well as the cost of maintenance and operation of tubes does not exceed that of a well made selective switch of the manual type shown in Figs. 2 and 4, and the circuits are simplified. Moreover, the radio switchboard equipped with such apparatus is more nearly in line with radio practice, as distinguished from telephone practice. If the A or filament battery circuit of, each tube be'disconnected except when receiving radio (assuming the'A batteries to be common) the plate filament circuit terminals of the line tubes such as 37 may be left permanently connectedtoline. The B battery, as well as the line, is protected by the space resistance in the plate circuit.

Referring particularly to Fig. 1, it will be observed that this represents the ordinary telephone exchange, of which there may be I one or several in a given local area served by some broadcastin relay station or studio. The same radio have its bus wires T, T, T extending into a number iof exchanges through cable, and

roadcasting station may in practice this or some equivalent arrangement is a necessity, since it would be badpractice to needlessly duplicate receiving and relaying apparatus at every telephone exchange. Regarding the telephone exchange with its line wires and subscribers stations as a complete wired entity, we may provide the necessary local bus wires, local receiving and relaying apparatus forradio, at the telephone exchange and then provide a central studio or relay station such as described hereinbefore, for all of the'associated groups of telephone central stations. The local receiving stations need not then be either complicated or powerful, and they would all be within the scope and control of the central studio and relay station. From each such local equipment however to and through the subscribers lines, all connec-' tions, supervision, control, testing, metering, and the like, would belong in the telephone administration typified by the diagram in Fig. 1. Furthermore, according to this very necessary arrangement, the maintenance and supervision of allwires and operation from the telephone exchange to and including the subscribers line, is for the telephone administration and particularly the wire chief and his assistants. Where there are several exchanges in the same area, all served by the same radio relay station and studio, there would be one wire chief for the area, with assistants at the different branch exchanges. It will then be understood that while the central studio from its own test boards would have access by wired trunk lines to each telephone exchange, and the receiving and relaying apparatus therein, this would be the limit for the studio, which would not have access to the subscribers lines for any purpose except ordinary connection as be tween one subscriber and another. Moreover, all that has been said about the general practice involved and modifications in the embodiment herein described, is to be understood as applying to both manual and automatic switching apparatus in either the telephone administration or the radio administration side of the system, or bothl I have chosen to illustrate herein as in prior applications copending herewith, standard manual Western Electric apparatus. The reason for this is that the circuits involved therein are standard in themselves, and when stripped of limitations ofform, are embodied without substantial change in either manual or automatic apparatus.

I believe all the modifications and all of the facts described herein by themselves and in combination, when employed in the manner described, are novel and original with 'me, I shall claim the same accordingly.

That phase of the invention involving me tering, disclosed but i not claimed herein, forms the subject matter of and is claimed claims hereinafter are to be understood as meaning a relay including as one element a vacuum tube or the equivalent thereof for relaying potential and current variations generated in accordance with sound waves, said current variations being adapted to act upon means to reproduce the original sound waves.

Reference is to, be had for gemeric claims to the program selecting and relaying features herewithin described, to applicants copending application S. No. 754,406, filed December 6, 1924:, the claims herein being directed to a system including a broadcast service station or district station, and the relaying, selecting, and amplifying features applied thereto.

What I claim is:

1. In a system of radio broadcast distribution, a broadcast service station, a tele-' phone central station with a plurality of subscribers statigns and individual wire lines interconnecting them, a wire line connecting the broadcast service station with the central station, and means at the central station individual to each subscribers line arranged to connect its associated line with the line leading from the broadcast service" station, said means including a telephonic relay for relaying sound waves, from said broadcast service line to its associated subscribers line.

2. In a system of radio broadcast distribution, a broadcast service station, a telephone central station with a plurality of subscribers stations and individual wire lines interconnecting them, a wire line connecting the broadcast service station with the central station, telephonic relay means at the central station individual to each subscribers line and means at the central station for connecting a .subscribers line through its associated telephonic relay means to the line leading from the service station. v

3. Ina system of radio broadcast distribution, a broadcast service station, a telephone central station with a plurality of subscrlbers stations and individual wire lines interconnecting them, a wire line connecting the broadcast service station with the central station, telephonic relay means at the central station individual to each subscribers line and means at the central station for connecting a snbscribers line through its associated telephonic relay means to the line leading from the, service station, together with means at each subscribers station for actuating said connecting means.

4. In a system of radio broadcast distribution, a broadcast service station, a telephone centralstation with a plurality of subscribers stations and individual wire lines interconnecting them, a wire line connecting the broadcast service station with the central station, telephonic relay means at the central station individual to each subscribers line, said telephonic relaying means consisting of vacuum tubes one for each line, at the central station and means whereby the input sides of said tubes may be connected at the central station with the line leading from the service station while the output side of each tube goes to its individual line.

5. In a system of radio broadcast distribution, a. broadcast service station, a telephone central station with a plurality of subscribers stations and individual wire lines interconnecting them, a wire line connecting the broadcast service station with the central station, telephonic relay means at the central station individual to each subscribers line, said telephonic relay means consisting of individual vacuum tubes, at the central station, means at the central station for connecting the individual tube relays with their input circuits to the line leading from the service station and their output circuits to their respective lines, and means at each subscribers station for individually controlling the connection of its tube relay at the central station.

6. In a system of radio broadcast distribution, a broadcast service station, a telephone central station with a plurality of subscribers stations and individual wire lines interconnecting them, a wire line connecting the broadcast service station with the central station telephonic relay means at the central station individual to each subscribers line and means at the central station for connecting a subscribers line through its associated telephonic relay means to the line leading from the service station, together with means at the central station for interconnecting the subscribers lines for conversation, and means at the subscribers stationfor difierentiating in signaling, and selective control between said interconnecting means and the means for connecting with the service station.

7. In a system of radio broadcast distribution, a broadcast service station, a telephone central station with a plurality of subscribers stations and individual wire lines intertion, and means to connect any subscriber through said second wire line from the central station to the modulator at the service station, for broadcasting.

, 8. In a system of radio broadcast distribution, a broadcast service station, a telephone central station with a plurality of subscribers stations and. individual wire lines interconnecting them, a wire line connecting the broadcast service station with the central station, telephonic relay means at the central station individual to each subscribers line and means at the central station for connecting a subscribers line through its associated telephonic relay means to said line leading from the service station, together with radio transmitting and modulating means therefor at the broadcast service station, a telephone line extending from the service station to the central station, a telephone set connected to said line at the service station whereby a subscriber at any of the substations may be connected through the central station for detecting. purposes with a party at the service station, and means at the service station for also operatively connecting the last mentioned service station line with the modulating means for broadcasting the conversation.

9. In a system of radio broadcast distribution, a broadcast service station, a telephone central station with subscribers stations and lines interconnecting them, program trunks between the service station and the central station, means at the broadcast station for transmitting different programs of broadcast matter over said program trunks to the central station, a telephonic relay at the central station associated with and individual to each subscribers line, and means controlled from the subscribers station for selectively connecting its-station with one of the program trunks through the said relay.

. 10. In a system of broadcast distribution, a broadcast servicestation, a telephone central station and subscribers substations with wired line circuits interconnecting them, a transmitter at the service station, a trunk line connecting the output of said transmitter'with'the central station, and a plurality of audion tube relays at the central station, one for each subscribers line having their input terminals arranged to be connected'to the said trunk in common and their output terminals adapted to be connected totheir 'ter with be central station, and a respective lines individually, together with switching means atthe central station for connecting said line tubes to said trunk, and means at subscribers station for controlling said switching means over their wire lines."

input terminals arranged to, be connected to' the said trunk in common and their output terminals adapted to be connected to their respective lines individually, together with automatic switching means controlled by the subscribers over their line circuits for connecting and disconnectmg their line tubes.

12. In a system of broadcast distribution,

a broadcast service station, a telephone central station with subscribers substations-and line circuits interconnecting them, a plurality of broadcast transmitters at the service station, trunk circuits connecting saidtransmitters with the central station, a plurality of audion tube relays at the central station, one for each subscribers line and automatic switching means controlled by the subscribers over their lines for selectively connecting the respective input circuits of their individual tubes to the said difl'erent trunks.

13. In a system of broadcast distribution, a broadcast service station, a telephone cening therein, a broadcast transmitter at the service stat 1on, a trunk circuit connecting the transmitter at the service station with tral station with subscribers lines terminatthe central station, and amplifying means'in the trunk circuit operatively connected between the trunk circuit and the subscribers line terminals arranged in stages increasing in both volume of'amplification and in number of units of amplification, the last set of signature.

. EDWARD E. CLEMENT. 

